Acute phase response to Mycoplasma haemofelis and 'Candidatus Mycoplasma haemominutum' infection in FIV-infected and non-FIV-infected cats

New records, and molecular detection of vector-borne pathogens in Felicola subrostratus from eastern Mexico

The study of lice associated with domestic cats is a neglected area of veterinary parasitology. In particular, the presence of the cat louse Felicola subrostratus, a small Ischnoceran species found in the fur of the domestic cat, is rarely recognized. In America, this species has been reported across six countries. Although it was also recently reported in Mexico, no studies on the molecular identification of the specimens or the monitoring of potential bacterial, and protozoan pathogens have been carried out. Thus, this work aimed to collect, and identify lice associated with domestic and free ranging cats from the states of Veracruz and Tabasco, using amplification and sequencing of the mitochondrial cytochrome c oxidase subunit I (COI), and the ribosomal 18S rDNA genes, and to monitor selected vector-borne bacterial (Bartonella, Mycoplasma, and Rickettsia) and protozoan (Babesia, and Hepatozoon) agents. Only entire lice were used for molecular host and pathogen identification. Eighty-one lice, identified as F. subrostratus, were recovered from five infested cats, and 30 were selected for molecular identification and pathogen surveillance. Analysis of the COI and 18S rDNA partial sequences showed a similarity of 96.79%-100% with sequences of F. subrostratus from the US. Mycoplasma haemofelis and Hepatozoon canis DNA was detected in three and four samples, respectively. This work provides new collection locations for F. subrostratus, and the first sequences of the COI and 18S rDNA genes from Mexico. It also reports two pathogenic microorganisms found in the lice.

Acute phase proteins and total antioxidant capacity in free-roaming cats infected by pathogenic leptospires

BACKGROUND

Leptospirosis is a neglected but widespread zoonotic disease throughout the world. Most mammals are hosts of Leptospira spp., including domestic cats, species in which no consensus has been reached on the clinical presentation or diagnosis of the disease. The study of acute-phase proteins (APPs) and biomarkers of oxidative status would contribute to knowledge about the disease in cats. This report evaluated four APPs: Serum amyloid A-SAA, Haptoglobin-Hp, albumin and Paraoxonase 1-PON1 and the antioxidant response through Total Antioxidant Capacity-TAC, in 32 free-roaming cats. Cats were classified as seroreactive for anti-leptospiral antibodies (group 1, n = 8), infected with Leptospira spp (group 2, n = 5) and leptospires-free cats (group 3, n = 19).

RESULTS

SAA differences were observed between groups 1 and 2 (p-value = 0.01) and between groups 2 and 3 (p-value = 0.0001). Hp concentration differences were only detected between groups 2 and 3 (p-value = 0.001). Albumin concentrations only differed between groups 1 and 3 (p-value = 0.017) and 2 and 3 (p-value < 0.005). Cats in groups 1 (p-value < 0.005) and 2 (p-value < 0.005) had lower PON1 concentrations than group 3. No statistically significant differences between pairs of groups were detected for TAC concentrations. The principal component analysis (PCA) retained two principal components, (PC1 and PC2), explaining 60.1% of the observed variability of the inflammatory proteins and the antioxidant TAC.

CONCLUSIONS

Increases in Serum SAA, Hp, and decreases in PON1 activity may indicate an active inflammatory state in infected cats (currently or recently infected).

Cat alpha-1-acid glycoprotein enzyme-linked immunosorbent assay: performance characteristics and reference intervals

OBJECTIVES

The aim of this study was to evaluate performance of a feline-specific ELISA for the measurement of alpha-1-acid glycoprotein (AGP) and to establish a reference interval (RI).

METHODS

Surplus serum samples with low (~200 µg/ml), medium (~450 µg/ml) and high (~745 and 930 µg/ml) AGP concentrations were used to assess the intra- and inter-assay coefficients of variation (CVs). The quality goal for bioanalytical method validation was a CV of <20%. Linearity was assessed by serial dilution of a sample with a high AGP concentration. Spike recovery was evaluated by mixing samples with low, medium and high AGP concentrations at different ratios. To establish the RI, residual serum samples from 51 healthy adult cats that were presented for health examinations or blood donation between August 2020 and June 2021 were included.

RESULTS

The intra-assay CV was 8.5%, 4.3% and 4.0%, and the inter-assay CV was 18.8%, 15.5% and 11.5% for serum samples with low, medium and high AGP concentrations, respectively. Excellent linearity (R2 = 0.98) was demonstrated for AGP concentrations ranging between 251.6 and 954.4 µg/ml. Average recovery was 95.0-99.7%. The right-sided RI for AGP was 328 µg/ml (90% confidence interval 300-354). Age had a statistically significant impact (increasing values with older age, P = 0.0026), but sex did not (P = 0.44), on AGP concentrations.

CONCLUSIONS AND RELEVANCE

The ELISA was accurate and showed acceptable precision with the modification of dilution used in this study. AGP concentrations in this population appeared to increase with increasing age.

Acute phase proteins in cats: Diagnostic and prognostic role, future directions, and analytical challenges

While clinical studies on acute phase proteins (APPs) have significantly increased in the last decade, and most commercial labs are now offering major APPs in their biochemical profiles, APP testing has not been widely adopted by veterinary clinical pathologists and veterinarians. Measurement of APP concentration is a useful marker for detecting the presence or absence of inflammation in cats with various diseases. APPs can also be reliably measured in different biological fluids (eg, effusions and urine) to improve their diagnostic utility. Measurement of APPs can be extremely beneficial in cats with feline infectious peritonitis (FIP) to discriminate between FIP and non-FIP cats with similar clinical presentations. Additional benefits come from multiple and sequential measurements of APPs, particularly in the assessment of therapeutic efficacy. APPs are more sensitive than WBC counts for early detection of inflammation and to demonstrate an early remission or recurrence of the diseases. Given the potential utility of APPs, more studies are warranted, with a particular focus on the applications of APPs to guide the length of antimicrobial therapies, as suggested by the antimicrobial stewardship policy. New inflammatory markers have been discovered in human medicine, with a higher specificity for distinguishing between septic versus nonseptic inflammatory diseases. It is desirable that these new markers be investigated in veterinary medicine, to further test the power of APPs in diagnostic setting.

Comparative evaluation of acute phase proteins by C-reactive protein (CRP) and serum amyloid A (SAA) in nonhuman primates and feline carnivores

The feasibility of a commercially available assay for C-reactive protein (CRP, CRP for humans: hCRP, and CRP for dogs: vCRP) and a trial reagent of serum amyloid A (SAA, vSAA for animals) were applied to the measurement of acute phase proteins in zoo animals, particularly in nonhuman primates and feline carnivores was evaluate. Results showed that hCRP and vSAA methods were applicable to measure CRP and SAA in Haplorhini. There was a highly significant correlation between both parameters with remarkably high correlation coefficient. A higher proportion of Bonnet macaques in Haplorhini, and the linear regression with good correlation between hCRP and vSAA levels were observed. Reference values in healthy Bonnet macaques were hCRP (46.86 ± 30.97 nmol/L) and vSAA (9.06 ± 1.95 μg/mL). Although Ring-tailed lemur, which belonging to Strepsirrhini, showed low vSAA concentrations (reference values: 1.08 ± 0.47 μg/mL), vSAA in patients was apparently elevated. The vCRP and vSAA methods were applicable to measurements of CRP and SAA in feline carnivores for highly significant correlation between both parameters. Theses two methods were also been deteded in lions, tigers and cheetahs. vSAA assays can be applied to measure SAA levels in other carnivores and herbivores. In conclusion, vSAA systems have potential utility as diagnostic tools for health screening and prediction in zoo animals.

Alpha-1 Acid Glycoprotein Reduction Differentiated Recovery from Remission in a Small Cohort of Cats Treated for Feline Infectious Peritonitis

Feline infectious peritonitis (FIP) is a systemic immune-mediated inflammatory perivasculitis that occurs in a minority of cats infected with feline coronavirus (FCoV). Various therapies have been employed to treat this condition, which was previously usually fatal, though no parameters for differentiating FIP recovery from remission have been defined to enable clinicians to decide when it is safe to discontinue treatment. This retrospective observational study shows that a consistent reduction of the acute phase protein alpha-1 acid glycoprotein (AGP) to within normal limits (WNL, i.e., 500 μg/mL or below), as opposed to duration of survival, distinguishes recovery from remission. Forty-two cats were diagnosed with FIP: 75% (12/16) of effusive and 54% (14/26) of non-effusive FIP cases recovered. Presenting with the effusive or non-effusive form did not affect whether or not a cat fully recovered (p = 0.2). AGP consistently reduced to WNL in 26 recovered cats but remained elevated in 16 cats in remission, dipping to normal once in two of the latter. Anaemia was present in 77% (23/30) of the cats and resolved more quickly than AGP in six recovered cats. The presence of anaemia did not affect the cat’s chances of recovery (p = 0.1). Lymphopenia was observed in 43% (16/37) of the cats and reversed in nine recovered cats but did not reverse in seven lymphopenic cats in the remission group. Fewer recovered cats (9/24: 37%) than remission cats (7/13: 54%) were lymphopenic, but the difference was not statistically different (p = 0.5). Hyperglobulinaemia was slower than AGP to return to WNL in the recovered cats. FCoV antibody titre was high in all 42 cats at the outset. It decreased significantly in 7 recovered cats but too slowly to be a useful parameter to determine discontinuation of antiviral treatments. Conclusion: a sustained return to normal levels of AGP was the most rapid and consistent indicator for differentiating recovery from remission following treatment for FIP. This study provides a useful model for differentiating recovery from chronic coronavirus disease using acute phase protein monitoring.

Analytical Validation of Two Point-of-Care Assays for Serum Amyloid A Measurements in Cats

Serum Amyloid A (SAA) is one of the most sensitive tests to detect inflammation in cats. In this study, two point-of-care assays for SAA measurements in cats (FUJI DRI-CHEM IMMUNO AU CARTRIDGE vf-SAA (method A), and CUBE-VET analyser (Method B), were analytically evaluated. Regarding the imprecision precision only the method A showed intra-assay and inter-assay CV < 10% at all concentrations. Both assays showed linearity with r close to 1 and the recovery were in the range of 81-112% for assay A and 85-125% for assay B and the limit of detection were 3.75 and 0.5 mg/dL for method A and B, respectively. A previously validated method for SAA quantification SAATIA; LZ-SAA (method C) was used as gold-standard to evaluate the accuracy of the assays. Significant correlations (p < 0.0001) were found between assays A and C (r = 0.94) and B and C (r = 0.91). In addition, an overlap performance test was made using serum samples from cats with non-inflammatory and cats with inflammatory. Both assays showed higher median SAA concentrations in cats with inflammatory diseases than in cats without inflammatory diseases (p < 0.0001). In conclusion, this manuscript provides data about the possible application of two point-of-care assays for the measurement of SAA concentration in cats.

Review of clinical aspects, epidemiology and diagnosis of haemotropic Mycoplasma ovis in small ruminants: current status and future perspectives in tropics focusing on Malaysia

Mycoplasma ovis (formerly Eperythrozoon ovis) is an epierythrocytic parasitic bacterium of small ruminants known as haemotropic mycoplasma, which is transmitted mechanically by biting flies and contaminated instruments. Acute mycoplasmosis causes severe haemolytic anaemia and mortality in young animals. At the same time, chronic disease may produce mild anaemia and varying degrees of morbidity depending on several factors, including age, reproductive status, the plane of nutrition, immunological status and the presence of concurrent infection. Haemotropic Mycoplasma ovis is currently recognised as an emerging zoonotic pathogen which is widely distributed in the sheep and goat producing areas of tropics and subtropics, where the disease is nearly endemic. Human infection has been reported in pregnant women, immunocompromised patients and people exposed to animals and arthropods. The current diagnosis of haemoplasma relies on microscopic evaluation of Giemsa-stained blood smear and PCR. Although there are few published reports on the incidence of haemotropic Mycoplasma ovis infection of small ruminants in Malaysia, information on its prevalence, risk factors, severity and economic impacts is grossly inadequate. Therefore, a large-scale survey of small ruminant flocks is necessary to elucidate the current seroprevalence status and molecular characteristics of haemotropic M. ovis infection in Malaysia using ELISA and PCR sequencing technologies. In the future, surveillance programs, including vector forecast, quarantine, monitoring by periodic surveys and public enlightenment, will limit the internal and transboundary spread of M. ovis, enhance control efforts and mitigate production losses in Malaysia.

A Clinical Investigation on Serum Amyloid A Concentration in Client-Owned Healthy and Diseased Cats in a Primary Care Animal Hospital

Although measurement of serum amyloid A (SAA) concentration in client-owned cats has already been shown to be clinically useful, limited data are available on common diseases at primary care hospitals. In this study, we measured the SAA concentration in cats with various diseases and investigated their clinical significance using a primary care hospital as a population. We measured the SAA concentrations in healthy cats (n = 98) and those with various clinical signs (n = 444). The SAA concentrations in healthy cats did not differ significantly by age, breed, sex, and presence/absence of neutering/spaying. The SAA concentrations were significantly higher in the diseased cat group than in the healthy cat group (p < 0.001). We observed significant increases in SAA concentrations in cats with confirmed diagnosis of inflammatory disease such as upper respiratory tract infections (p < 0.001), pneumonia (p < 0.001), pyometra (p = 0.001), and feline infectious peritonitis (p < 0.001), compared with those observed in healthy cats. Conversely, no increase was observed in cardiomyopathy, hyperthyroidism, and diabetes mellitus without systemic inflammation. In univariate analysis, survival at 30 days (p = 0.03) differed significantly between the low and high SAA concentration groups, but not at 180 days. In multivariate analysis, survival at 30 days did not significantly affect SAA concentration. Measurement of SAA concentration is a useful biomarker for detecting the presence or absence of inflammation in diseased cats. However, it may not be useful as a biomarker for determining the prognosis of the disease.

Concomitant feline immunodeficiency virus (FIV) and Mycoplasma haemofelis in a barn cat

A 5-year-old male barn cat was presented with lethargy and excessive bleeding following castration. The patient developed hemolytic anemia and diagnostic tests revealed infection with feline immunodeficiency virus and Mycoplasma haemofelis. This case serves as a reminder of the importance of testing for infectious diseases and educating owners on feline infectious disease prevention and management.

Acute phase proteins response in cats naturally infected by hemotropic mycoplasmas

Information about the acute phase proteins (APP) response in cats naturally infected with hemoplasmas and in cats co-infected with different species of hemoplasmas is lacking. This study evaluated serum amyloid A (SAA), haptoglobin (Hp) and albumin in 48 cats naturally infected with hemoplasmas, including 25 with Candidatus Mycoplasma haemominutum and 23 co-infected with different hemoplasmas agents; and in 10 healthy control cats. Infected cats had significantly higher Hp and lower albumin than controls. Symptomatic cats had significantly higher SAA and Hp, and lower albumin than asymptomatic animals, and also than controls. Asymptomatic cats had significantly higher Hp than controls. Concentrations of APP were not significantly different between single infected and co-infected cats. According with these results, hemoplasmosis should be considered when alterations in APP are detected in diseased cats with compatible clinical signs. Furthermore, a subclinical infection should be considered in apparently healthy cats from endemic areas with increased Hp.

Serum acute phase proteins in Dirofilaria immitis and Wolbachia seropositive cats

Objectives The aim of this study was to characterise the response of acute phase proteins (APPs) in cats seropositive for Dirofilaria immitis and to its endosymbiont bacterium Wolbachia. Methods The APPs serum amyloid A (SAA), haptoglobin (Hp) and ceruloplasmin (Cp) were measured in 25 seropositive cats and in 16 healthy seronegative cats. Results SAA and Cp concentrations were significantly higher in animals with D immitis seropositivity that exhibited clinical signs related to the disease, and Hp was elevated in all D immitis-seropositive animals. There was no significant correlation between APPs and D immitis or Wolbachia species antibody titres. Conclusions and relevance An association between feline seropositivity to D immitis and APP response was demonstrated. Increases in serum SAA and Cp concentrations were related to D immitis-associated clinical signs, whereas Hp increased in all seropositive animals.

Acute phase proteins response in cats naturally infected with Hepatozoon felis and Babesia vogeli

BACKGROUND

The measurement of acute phase proteins (APP) is being increasingly used in human and veterinary medicine in diagnosis, prognosis, treatment monitoring, and in general health screening. However, information about the APP response in cats infected with agents of vector-borne diseases is lacking.

OBJECTIVES

The purpose of the study was to investigate the concentrations of serum amyloid A (SAA), haptoglobin (Hp), and paraoxonase-1 (PON1) in cats naturally infected with Hepatozoon felis and Babesia vogeli.

METHODS

Serum concentrations of SAA, Hp, and PON1 were determined in 19 cats naturally infected with H felis and in 11 cats naturally infected with B vogeli, and compared to concentrations in 10 healthy control cats.

RESULTS

Serum Hp concentrations were significantly increased, and PON1 concentrations significantly decreased in symptomatic and asymptomatic cats infected with H felis and B vogeli when compared with healthy noninfected cats. In the H felis-infected population, concentrations of SAA and Hp were significantly increased in symptomatic cats when compared with asymptomatic animals.

CONCLUSIONS

This study demonstrated differences in APP concentrations in cats infected with H felis and B vogeli. Therefore, Hp and PON1 concentrations could be helpful in discriminating healthy cats from cats with asymptomatic or symptomatic infection by these agents.

Validation of an enzyme-linked immunosorbent assay for measurement of feline haptoglobin

Haptoglobin is a positive moderate acute phase protein (APP) in cats. Measurement of haptoglobin can be used in the diagnosis, prognosis, and monitoring of systemic inflammatory disease, especially by creating profiles with major APPs. The aim of our study was to validate a sandwich enzyme-linked immunosorbent assay (ELISA) for measurement of feline haptoglobin. The validation included an assessment of precision, accuracy, detection limit, method comparison with a spectrophotometric assay, and evaluation of the overlap performance. The concentration of haptoglobin was measured in serum from 27 healthy and 23 sick cats. The coefficients of variation were 2.5–4.7% for intra-assay variability and 7.1–11.6% for interassay variability. The ratio of observed to expected dilutional parallelism of 4 serum samples was 108.1–118.4%. The ratio of observed to expected spike recovery of 4 serum samples was 90.8–94.0%. The lower detection limit was 0.19 g/L. Method comparison revealed a positive correlation ( rs = 0.949, P < 0.0001) and a proportional bias between the methods of −38.9%. Agreement between the methods was not clinically acceptable. Overlap performance of the ELISA was deemed satisfactory. The sandwich ELISA measures feline haptoglobin with an analytical and overlap performance acceptable for clinical purposes. Given the observed bias, the ELISA cannot be used interchangeably with the spectrophotometric assay.

Association between feline immunodeficiency virus (FIV) plasma viral RNA load, concentration of acute phase proteins and disease severity

Veterinarians have few tools to predict the rate of disease progression in FIV-infected cats. In contrast, in HIV infection, plasma viral RNA load and acute phase protein concentrations are commonly used as predictors of disease progression. This study evaluated these predictors in cats naturally infected with FIV. In older cats (>5 years), log10 FIV RNA load was higher in the terminal stages of disease compared to the asymptomatic stage. There was a significant association between log10 FIV RNA load and both log10 serum amyloid A concentration and age in unwell FIV-infected cats. This study suggests that viral RNA load and serum amyloid A warrant further investigation as predictors of disease status and prognosis in FIV-infected cats.

Prevalence and risk factor analysis of feline haemoplasma infection in New Zealand domestic cats using a real-time PCR assay

Haemotropic mycoplasmas (haemoplasmas) are small epierythrocytic bacteria that have the potential to cause severe, life-threatening haemolytic anaemia. The aim of the current study was to evaluate feline haemoplasma prevalence using real-time polymerase chain reaction (PCR) from a convenience sample of New Zealand domestic cats, including blood film examination and a risk factor analysis. DNA was extracted from 200 blood samples submitted to a diagnostic laboratory for routine haematology over a 12-month period. Species-specific real-time PCR assays identified 62 cats that were positive for haemoplasma DNA, giving an overall prevalence of 31%. Twelve of the positive cats had dual infections. The prevalence of the three feline haemoplasmas was 25% for 'Candidatus Mycoplasma haemominutum', 7.5% for Mycoplasma haemofelis and 4.5% for 'Candidatus Mycoplasma turicensis' (CMt). All samples were positive for an internal control (feline 28S rDNA) by real-time PCR. Sensitivity and specificity of blood smear examination for haemoplasma infection in this study was 9.7% and 97.8%, respectively. Retroviral infection was tested using the Idexx Snap Feline Triple test on all samples. Twenty cats (10%) were feline immunodeficiency virus (FIV) positive and 11 cats (5.5%) were feline leukaemia virus (FeLV) positive. Statistical comparisons, using multivariate logistic regression, indicated that positive FIV status, male gender and non-pedigree breed were significantly (P <0.05) associated with haemoplasma infection, with odds ratios of 10.16, 5.04 and 3.03, respectively. The results of this study demonstrate the prevalence of the three main feline haemoplasma species in New Zealand for the first time, with prevalences correlating with previous overseas studies. This is the first report of CMt in New Zealand.

Monitoring acute phase proteins in retrovirus infected cats undergoing feline interferon-ω therapy

OBJECTIVES

Recombinant feline interferon-ω therapy is an immunomodulator currently used in the treatment of different retroviral diseases including feline immune deficiency virus and feline leukaemia virus. Although its mechanism of action remains unclear, this drug appears to potentiate the innate response. Acute phase proteins are one of the key components of innate immunity and studies describing their use as a monitoring tool for the immune system in animals undergoing interferon-ω therapy are lacking. This study aimed to determine whether interferon-ω therapy influences acute phase protein concentrations namely serum amyloid-A, α-1-glycoprotein and C-reactive protein.

METHODS

A single-arm study was performed using 16 cats, living in an animal shelter, naturally infected with retroviruses and subjected to the interferon-ω therapy licensed protocol. Samples were collected before (D0), during (D10 and D30) and after therapy (D65). Serum amyloid-A and C-reactive protein were measured by specific enzyme-linked immunosorbent assay kits and α-1-glycoprotein by single radial immunodiffusion.

RESULTS

All the acute phase proteins significantly increased in cats undergoing interferon-ω therapy (D0/D65: P<0·05) CLINICAL SIGNIFICANCE: Acute phase proteins appear to be reasonable predictors of innate-immune stimulation and may be useful in the individual monitoring of naturally retroviral infected cats undergoing interferon-ω therapy.

Rapid detection of haemotropic mycoplasma infection of feline erythrocytes using a novel flow cytometric approach

Background

The haemotropic mycoplasmas Mycoplasma haemofelis and Candidatus Mycoplasma haemominutum cause feline infectious anaemia with infection rates in feline populations reflecting widespread subclinical infection. Clinically significant infections are much rarer but can be life-threatening. Current diagnosis is dependent upon visualising organisms in stained blood smears, PCR or quantitative PCR (qPCR). These procedures are labour-intensive and time-consuming. Furthermore, PCR-based approaches offer limited insight into the disease burden of the infected animal.

Methods

We have developed a novel and rapid flow cytometric system that permits diagnosis of haemotropic mycoplasma infections and quantitation of the percentage of erythrocytes that are parasitized. The method exploits the fact that mature mammalian erythrocytes, the host cell for haemoplasmas, are enucleated and thus lack nucleic acid. DRAQ5 is a synthetic anthrocycline dye which rapidly crosses cell membranes and binds to nucleic acids. The presence of exogenous bacterial DNA in mammalian erythrocytes can, therefore, be detected by DRAQ5 uptake and flow cytometric detection of DRAQ5 fluorescence.

Results

Here, we show that this system can detect epi-erythrocytic infection of companion felines by haemotropic mycoplasma. Due to their differences in size, and hence the quantity of DNA, the two major feline hemoplasmas M. haemofelis and Candidatus M. haemominutum can be distinguished according to DRAQ5 fluorescence. We have also shown the usefulness of DRAQ5 uptake in monitoring a cat infected with M. haemofelis sequentially during treatment with doxycycline.

Conclusions

The technique described is the first report of a flow cytometric method for detecting haemotropic mycoplasmas in any species and could be applied to widespread screening of animal populations to assess infection by these epi-erythrocytic parasites.

Amyloidosis in association with spontaneous feline immunodeficiency virus infection

Tissues from 34 naturally feline immunodeficiency virus (FIV)-infected cats, 13 asymptomatic cats and 21 cats with signs of feline acquired immunodeficiency syndrome (F-AIDS), and 35 FIV-seronegative subjects were examined to determine the presence of amyloid deposits. Twenty experimentally FIV-infected cats and five specific pathogen-free (SPF) control cats were also included in the study. Paraffin-embedded sections from kidney and other organs were submitted to histological and histochemical analysis. Amyloid deposits were identified by a modified Congo red stain and confirmed by electron microscopy to demonstrate the presence of amyloid fibrils in amyloid positive glomeruli. In all positive cases, secondary amyloidosis was identified with potassium permanganate pretreatment and amyloid type was further characterised by immunohistochemistry using primary antibodies against human AA and feline AL amyloids. Amyloid deposits were present in different tissues of 12/34 (35%) naturally FIV-infected cats (seven presenting F-AIDS and five in asymptomatic phase) and in 1/30 FIV-seronegative cats. All the experimentally FIV-infected and SPF subjects showed no amyloid deposits. Amyloidosis has been reported in human lentiviral infections, and the data reported here demonstrate the need, in naturally FIV-infected cats, to consider the presence of amyloidosis in differential diagnosis of hepatic and renal disorders to better assess the prognosis of the disease.